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Bio Lecture 01 Water, Enzymes & Biological Molecules for IMAT Biology | Full Concept + MCQs — Transcript

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0:02Hello everyone.
0:04Welcome to IMAT Tutor.
0:05In this lecture, we are starting IMAT
0:07biology from the very foundation.
0:11Water, biological molecules, pH,
0:13buffers, and enzymes.
0:16These topics look basic, but IMAT does
0:19not test them in a basic way.
0:22IMAT will test definition,
0:24then exact wording, and cause-effect
0:27logic.
0:28If you understand the patterns in this
0:30lecture,
0:31you will score marks almost
0:32automatically. So, watch carefully and
0:35do not memorize blindly.
0:37Understand how IMAT thinks.
0:41First part
0:43will be about
0:45water
0:47and
0:49hydrogen bonding.
0:53This is an IMAT favorite concept.
0:56And we, first of all, need to know why
0:59water is special.
1:02IMAT repeatedly ask one simple idea in
1:05different forms. Which property of water
1:08explains a biological phenomenon?
1:12So, you must link property to function.
1:15Now, explain slowly.
1:17Water is special because it is a polar
1:20molecule.
1:23Back in our chemistry lecture, we
1:24studied that oxygen is highly
1:27electronegative,
1:29and hydrogen is less electronegative.
1:32So, the oxygen side becomes partially
1:34negative,
1:36and the hydrogen side becomes partially
1:38positive.
1:40This polarity allows hydrogen bonding.
1:44Now, list properties with IMAT logic.
1:47First of all, high specific heat
1:49capacity.
1:51Due to hydrogen bonding,
1:53water absorbs a lot of heat with only a
1:57small temperature rise. This stabilizes
2:00body temperature.
2:02Number two, high latent heat of
2:05vaporization.
2:06A large amount of energy is required to
2:09convert liquid water into vapor.
2:12IMET loves this exact example. Number
2:15three, cohesion and adhesion.
2:19What do we mean by cohesion and
2:20adhesion?
2:23They're basically the same.
2:26It means the molecules sticking to
2:28water.
2:29Cohesion holds water molecules together.
2:32I mean, cohesion will hold water
2:35molecules together. Let's say like this.
2:37And adhesion allows water to stick to
2:40surface.
2:41All right? So, this is the particular
2:43difference that we need to know about
2:45cohesion and adhesion.
2:48And the fourth phenomenon that we need
2:51to understand is that ice is less dense
2:54than liquid water.
2:55So, let's say we denote the density with
2:58row, the density of ice is less than the
3:03density of liquid water.
3:07And what would be the IMET pattern that
3:09we need to know?
3:11In IMET, there will be a question like
3:14which property explains X? You must
3:18instantly map phenomenon to property.
3:21What we have learned, let's review them
3:24in our lecture.
3:27We have talked about the specialty about
3:29water.
3:30We have talked the polarity and hydrogen
3:32bonding.
3:33And due to this hydrogen bonding, the
3:35high specific heat capacity, high latent
3:39heat of vaporization, cohesion, and
3:41adhesion.
3:42And also we have said that ice has less
3:45density than liquid water. And the IMET
3:48pattern, we have also discussed that.
3:53An example can be cooling by sweating is
3:56mainly explained by latent heat of
3:59vaporization. So, whenever we are asked
4:01about the latent heat of vaporization,
4:04we need to remember the cooling of our
4:07body by the process of sweating.
4:11Okay.
4:13Our next topic, our next section will
4:15discuss about hydrogen bonding.
4:19IUPAC has a very specific definition and
4:22say clearly that a hydrogen bond is an
4:25attraction between an hydrogen atom that
4:28is already covalently bonded to a
4:30strongly electronegative atom and a lone
4:33pair on another electronegative atom in
4:36a different molecule.
4:38To understand the definition, let's
4:40consider
4:41hydrogen.
4:44Then,
4:46we need to have
4:48an electronegative atom. It can be
4:50fluorine, oxygen, or nitrogen. Let's
4:53take fluorine.
4:55And the final condition is
4:58the fluorine needs to have lone pair.
5:02So, if these three conditions are met,
5:05we will see hydrogen bonding.
5:07And we have already said that
5:09electronegative atoms are nitrogen,
5:12oxygen, or fluorine.
5:14There's an important trap.
5:16Hydrogen bond is not the covalent bond
5:19inside the water molecule.
5:21Actually, it is an intermolecular
5:23attraction.
5:25Remember, intermolecular and
5:28intramolecular, they are different.
5:31Intramolecular means inside the
5:33molecule.
5:35But, intermolecular means between two
5:38molecules. That's why hydrogen bond is
5:43an intermolecular force.
5:48Right? And I might frequently test this
5:51confusion.
5:53So,
5:54this was the hydrogen bond that we were
5:56talking about. Hydrogen bond must have
6:00hydrogen atom
6:02and electronegative atom and a lone
6:05pair.
6:07Right? And we have discussed the trap
6:10that hydrogen bond is not a covalent
6:13bond inside the water molecule. Rather,
6:16it is a bond between molecules.
6:21Okay.
6:22Now,
6:23let's go to part two, where we will
6:25discuss biological molecules.
6:30So,
6:31if we want to talk about biological
6:33molecules,
6:35then the first thing that will come to
6:37our discussion will be
6:40carbohydrate.
6:42All right?
6:44So, what is carbohydrate?
6:46Carbohydrates
6:48are built from monosaccharide.
6:51To understand monosaccharide, you must
6:54understand that monosaccharides
6:57are made up of carbon, hydrogen, and
7:00oxygen.
7:01There will be a particular ratio among
7:04these three atoms.
7:06The ratio of carbon, hydrogen, and
7:08oxygen would be 1:2:1.
7:13And monosaccharide has different types
7:17based on the number of carbons. If there
7:19are three carbons, it will be triose.
7:22Gradually, if there will be six carbon,
7:25we will call it hexose.
7:27Hexose is very important.
7:30And when we call hexose, that means it
7:33has six carbon atoms.
7:35Right?
7:37So,
7:38if two monosaccharides, let's say, are
7:41getting attached, the bond will be
7:44called glycosidic bond.
7:46And we will get disaccharide, right?
7:50Disaccharide.
7:53And if we attached more than
7:5710 monosaccharides,
7:59then we will call it polysaccharide.
8:03There's another term called
8:05oligosaccharide.
8:09And in case of oligosaccharide, the
8:11number of monosaccharide would be
8:15less than 10.
8:16All right.
8:18And what is the key IMAT rule that we
8:20need to understand?
8:22When monosaccharides join, they form
8:26glycosidic bonds by condensation that we
8:29have discussed.
8:31And
8:33we need to say another thing.
8:35Each glycosidic bond formation removes
8:38one water molecule.
8:40Let's put that into practice.
8:43A common disaccharide example is
8:46sucrose.
8:49Sucrose is formed by glucose
8:53and fructose.
8:56What are their formulas? Glucose is
8:58C6H12O6.
9:01Same goes for fructose, C6H12O6.
9:05If we add them together, it was supposed
9:08to be like C12 H24O12.
9:13But
9:14due to a bond being formed between
9:16glucose and fructose, we need to
9:18subtract one molecule of water.
9:22And finally, the formula of sucrose
9:25would be C12
9:27H22O11.
9:30This is extremely testable.
9:33If a polysaccharide, on the other hand,
9:36contains n glucose units, and we will
9:39write it like this. First of all, we
9:41would write the formula of glucose
9:43C6H12O6.
9:47And initially, we would minus a water
9:50molecule from it. It will become like
9:52this, C6H5.
9:56Actually, not H5.
10:05C6
10:07H10O5.
10:10And we will put n with the whole
10:12bracket. And this structure is called
10:16polysaccharide.
10:20This logic appears every year. Right?
10:24Okay. Monosaccharide
10:26means glucose or pentose or triose or
10:31tetrose. Right? Where the ratio is
10:361:2:1.
10:39And disaccharide, when we are forming
10:41disaccharide, we need to put two
10:43monosaccharides together, and there will
10:46be a condensation reaction, which will
10:48subtract one water from the formula.
10:51And we have also discussed
10:53polysaccharide, where many
10:55monosaccharides are joined by glycosidic
10:57bonds. And if we want to write the
10:59formula of it, we need to write it like
11:02this. First, we will write the glucose
11:04formula C6H12O6,
11:06then minus one water molecule.
11:09And this will be like C6H10O5,
11:13then put n. That's why it is said that
11:16if a polysaccharide contains n glucose
11:19units, number of water molecules lost is
11:23n minus one. All right? Very important
11:28topic it was. Now, let's go
11:31to our next topic. But, before the next
11:34topic, let's
11:36also uncover this condensation rule.
11:39Each glycosidic bond formation removes
11:41one water molecule.
11:43It was already mentioned.
11:45Okay.
11:46Our next topic is lipid. We would put
11:482.2 for it.
11:52What is lipid or what are lipids?
11:55Lipids are hydrophobic molecules. That
11:58means they hate water. They don't want
12:00to react with water and they are not
12:02water soluble.
12:04And when we break down lipid,
12:08lipid is formed by triglyceride.
12:13So, let's write it like this.
12:17Inside a triglyceride, we will have one
12:20glycerol
12:23and
12:25three fatty acids.
12:32And the bond formed between them, this
12:35bond is called ester bonds.
12:40In glycerol, there will be presence of
12:43three OH groups. This is also important
12:46for the test.
12:48And fatty acid, fatty acid has a
12:50functional group and that functional
12:52group is C double O H.
12:55Right?
12:57Then the next important topic in lipid
13:00section is phospholipid.
13:02Phospholipids form cell membranes.
13:06Very important for us. If we discuss the
13:09cell membrane, we know that cell
13:12membrane is formed of phospholipid
13:14bilayer.
13:16And it has
13:19head and tail.
13:21Right? The head is hydrophilic.
13:25That means it loves water and it is
13:28soluble in water. The tail, this is
13:31hydrophobic.
13:33This is very much asked in the exams, so
13:36we need to remember it just the way it
13:38is.
13:39And
13:40I might test the recognition questions
13:44like this. Which part interacts with
13:46water? The answer would be the phosphate
13:49head. And which part avoids water? The
13:52answer would be hydrophobic tail.
13:55Right?
13:56So, this is written in our lecture note.
14:00Right?
14:02In case of lipid,
14:05we have said lipid is glycerol and three
14:08fatty acids and the bonds between them
14:10will be ester bonds. And in case of
14:13phospholipid, phospholipid is found
14:15mainly in membrane formation. Right? The
14:18head would be hydrophilic and the tail
14:20will be hydrophobic.
14:21The key concept, hydrophobic regions in
14:24membrane molecules are frequently
14:25tested. This the key concept,
14:27recognition type. Hydrophobic regions
14:30are the tail and the head is
14:33hydrophilic. All right? Now, let's go to
14:36the topic of protein.
14:39To understand protein, we need to
14:41understand amino acid.
14:43So, proteins are made up of so many
14:46amino acids together.
14:48How does an amino acid look like?
14:51It will have a carbon, it will have a
14:53carboxylic acid. It will also have an
14:56amino group.
14:58Then, hydrogen can be there and an alkyl
15:01group. This is the common formation of
15:04an amino acid. Amino acids are joining
15:06together, it will make peptide.
15:10And the peptide will formed polypeptide.
15:14And polypeptide
15:17eventually will form protein molecules.
15:21Right?
15:22So,
15:23we can say from our lecture that
15:26proteins are built from amino acids
15:29joined by the peptide bonds. Very
15:30important, and this reaction is also
15:33type of condensation
15:35reaction.
15:36And proteins has structural levels. One
15:40is primary, another one is secondary,
15:43tertiary, and quaternary.
15:45Sometimes primary can be addressed as
15:481°, secondary 2°, this is 3°, and this
15:51is 4°.
15:53What are the high yield links?
15:56There are some high links such as active
15:59site shape, denaturation, and enzyme
16:02specificity. What do we mean by this? If
16:06we decrease the pH, then the protein
16:09will get
16:10misfolded, and it will lose its
16:13functionality.
16:14If we increase the temperature, the
16:17protein might get coagulated,
16:19or it can become denatured.
16:22And also in case of enzyme,
16:24we must know enzymes are nothing but
16:28proteins.
16:29And there is a particular temperature
16:31range,
16:33in which range proteins will act
16:35superiorly and optimally.
16:38But if we increase the temperature too
16:40much or decrease it, then the enzyme
16:43will not work properly. And when we say
16:46that specificity,
16:48it means that
16:50for each chemical reaction, there will
16:52be a specific enzyme. Enzymes don't work
16:55in all the reactions. There will be some
16:57specific reactions reserved for it.
17:01All right?
17:02Now, our next topic,
17:05an exam favorite topic, that is nucleic
17:08acid.
17:11And
17:13if we want to understand nucleic acid,
17:15then we must know nucleic acid is a
17:18polymer
17:20of
17:24nucleotide.
17:28All right?
17:30So,
17:31in nucleotide, there will be two other
17:33components. One will be phosphate.
17:38Another will be nucleoside.
17:44Nucleoside has base and sugar.
17:51And the sugar
17:53that we are talking about in this will
17:55be
17:56ribose.
17:57If the sugar is found in RNA,
18:01then it will be ribose
18:05or
18:06C5H10O5.
18:11If we want to see the sugar inside DNA,
18:15then it will become deoxyribose.
18:18That means it will have one less oxygen
18:21in its formation.
18:23So, deoxyribose
18:26will be written like this.
18:28Deoxyribose and it will be C5H10O4.
18:33Very important to remember this formula.
18:36What about the base? There are two types
18:38of base. One is purine.
18:41Another one is pyrimidine.
18:45The name
18:47that is larger, their structure will be
18:49smaller. In case of purine, the name is
18:52smaller, but their structure is larger.
18:55Purines are adenine and guanine.
18:58Pyrimidines are cytosine,
19:00thymine, uracil.
19:03Uracil is found in case of RNA.
19:05And cytosine thymine are found in case
19:09of DNA.
19:10And the bases has particular structure.
19:14Adenine will always attach or pair with
19:17thymine with two hydrogen bonds between
19:20them.
19:21Cytosine
19:22pairs with guanine with three hydrogen
19:26bonds.
19:28Right? And if we are asked about the
19:30backbone of DNA, we have seen DNA like
19:33this.
19:34The backbone of DNA will be formed by
19:37phosphodiester bonds.
19:40I met will ask about the percentage base
19:43composition.
19:44It will also ask about the counting of
19:47hydrogen bonds, counting phosphodiester
19:50bonds,
19:52and complementary strand sequences.
19:55These are the scoring questions.
19:57We will practice each of them when we
20:00will be practicing our MCQ section.
20:04Let's review what we have studied in
20:07nucleic acid section.
20:10Basic, but this nucleic acid will be
20:13asked every single year.
20:15We have already said
20:16in case of DNA,
20:18DNA will have deoxyribonucleic acid. It
20:22will have base pairing.
20:24And there will be hydrogen bonds between
20:27the bases, and the backbone will have
20:29phosphodiester bonds. Right? What are
20:33the questions that are important?
20:35The questions are the following.
20:37There will be some percentage base
20:39problems, then hydrogen bonds counting
20:42or phosphodiester bonds. Also,
20:44complementary strand sequence. We'll
20:46practice them. You don't need to worry
20:48about those.
20:50Then, after completing this section,
20:53let's move to part three.
20:55In part three, we will talk about the
20:57pH.
20:58Right? pH and buffer.
21:03What is pH?
21:06Basically, we mean pH is
21:09acidity
21:10or how many hydrogen ions are present in
21:12a solution. That is the simple concept.
21:16But when we try to mathematically
21:17express it,
21:19pH will be equal to
21:22minus log
21:27base 10 of hydrogen ion concentration.
21:33So, the trap is that pH is logarithmic.
21:39That means that a change of one pH,
21:42let's say from two to three,
21:45means a tenfold change
21:49in hydrogen ion concentration.
21:52Right? This is very important.
21:55An IMAT will test this logic directly.
21:59And this is the pH that we have
22:01discussed. After that, buffer.
22:04So, what is buffer?
22:06And why is buffer important?
22:09Because our body's blood circulation
22:12system has a certain pH and the pH range
22:15is 7.35
22:17to 7.45.
22:19And keeping this range preserved is very
22:23crucial.
22:24And keeping this range preserved is very
22:27crucial for our
22:29bodily functions. Okay. And how do we
22:32make sure that the range is preserved?
22:36Buffer comes into action.
22:38Buffer is a solution
22:40in which if you add some base
22:44or if you add some acid, it will try to
22:48resist
22:49the change in pH. But don't you think
22:53that you can add as many bases or acids
22:57as possible. You can only add a few
23:01bases or few acids, all right?
23:04And what is the formation of buffer?
23:06Buffer usually has a weak acid
23:12and its conjugate base.
23:16All right?
23:20Let's say a weak acid example can be
23:22this, CH3COOH.
23:26This is called acetic acid
23:29or ethanoic acid. If we remove the
23:32hydrogen from this compound, then we
23:34will find its conjugate base and it will
23:37be CH3COO.
23:40Right?
23:41It can also be the opposite. I mean, you
23:44can also form buffer by a weak base and
23:47its conjugate acid.
23:49And why I met cares about this? Because
23:52enzymes work only in a narrow pH range.
23:56Right?
23:58And one famous acid that is present
24:00inside our body is found in our stomach
24:03and that is hydrochloric acid.
24:07On the other hand,
24:09the small intestine, it doesn't have
24:11acid. It's rather alkaline.
24:14Very important to know.
24:16I met often links buffers with digestion
24:18and enzyme activity.
24:21HCL pH is less than seven solution. On
24:25the other hand, alkaline pH will be
24:28greater than seven. Right?
24:30And
24:32let's cover what we have studied till
24:34now. We have studied the pH and buffers.
24:37pH definition
24:39Actually, this means that pH is
24:42negative log
24:45hydrogen ion concentration
24:48and log to the base 10. And the trap is
24:51that pH scale is logarithmic.
24:54pH six has 10 times higher
24:57proton concentration or hydrogen ion
25:01concentration than pH 7. That means that
25:04pH 6 is more acidic than pH 7 or pH 6 is
25:1010 times more acidic than pH 7.
25:13We have also talked about the buffers.
25:15Buffer means buffer is a solution that
25:17will resist pH change. Usually, buffer
25:20is formed by weak acid conjugate base.
25:23We have given an example. Also, it can
25:25be formed by weak base and conjugate
25:27acid. If we remember these two rules,
25:29then we can solve any type of buffer
25:31solutions or we can identify at least.
25:34And why I'm at chaos, we have said that
25:37enzymes have narrow optimum pH ranges.
25:40Digestion has different pH zones
25:42such as stomach acid has
25:45hydrochloric acid. On the other hand,
25:48small intestine is alkaline. We have
25:50already covered that as well.
25:53Okay.
25:55Our next big topic is enzyme.
25:59Right? Enzyme is the most tested
26:02section. That's why enzyme is very very
26:05important for us.
26:07What are the functions of enzymes? We
26:09have already said enzyme is a type of
26:11protein. But you must remember enzymes
26:14are not always proteins. Sometimes
26:16enzymes can have non-protein parts as
26:19well.
26:21If an enzyme is formed by protein
26:26and non-protein, then we will not call
26:29it enzyme anymore. We will call it
26:31conjugated
26:34protein.
26:36All right?
26:37And in that case,
26:39in conjugated protein, the protein part
26:42will be called apoenzyme.
26:46And the non-protein part will be called
26:50prosthetic group.
26:57If the prosthetic group is any metal
27:00ion,
27:01then we will call it cofactor.
27:05And if the prosthetic group is any
27:08organic compound,
27:11we will call it
27:13coenzyme.
27:17One important distinction that we need
27:19to make is that enzyme works in a narrow
27:22temperature and pH range.
27:24That means that if you put too much
27:26temperature on enzyme, it will lose its
27:29functionality. But coenzymes, they can
27:32tolerate much heat and it can work in
27:35high temperatures.
27:37Right? High temperatures. This is
27:39important and this can be tested in the
27:42IMAT.
27:43Right?
27:45In other words, we can also say enzymes
27:48are called biocatalyst.
27:51Biocatalyst.
27:53Because enzymes help a reaction to move
27:57forward. It will help a reaction to move
28:00forward, but it doesn't participate in
28:03any reaction directly. And how does
28:06enzyme help a reaction move forward?
28:09Enzyme will decrease the activation
28:11energy. Right? This is very important.
28:15Enzyme will decrease the activation
28:18energy. What is activation energy?
28:20Let's say this is a reactant and it
28:23wants to become product.
28:25So,
28:27to
28:29complete this reaction, we must have a
28:32particular activation energy.
28:35But when we add the enzyme in this
28:38reaction, the activation energy
28:41or EA will decrease and the reaction
28:44will easily occur.
28:46And this is very high yield when it
28:48comes to the function of enzymes. They
28:52are not consumed in the reaction,
28:55right? And they increase the reaction
28:57rate by lowering activation energy. And
29:00what about the temperature and pH
29:02effects
29:03on enzyme?
29:05Let's explain the logic step by step.
29:08Let's say the temperature is increasing.
29:11If the temperature increases,
29:13then the molecules inside a compound, it
29:17will increase its kinetic energy. And if
29:20the kinetic energy increases, the
29:22collision between the atoms, the
29:24molecules will increase as well.
29:26And as a result, the rate of reaction,
29:29let's say the rate of reaction will also
29:31increase.
29:32But remember, there will be an optimum
29:35temperature. If you go beyond optimum
29:38temperature, then enzyme will denature
29:41and active site shape changes.
29:44Activity rapid to decreases. What do we
29:46mean by the active site? Let's say this
29:49is an enzyme.
29:50Enzyme has an active site, and
29:53let's say this is the active site, AS.
29:56This active site will bind with
29:58substrate. The substrate means reactant.
30:01Let's say with black block we mean a
30:05substrate. If the active site gets
30:08deactivated, then it will not
30:10participate in any reaction.
30:13And now talk about pH.
30:16If we change the pH, then the ionization
30:19of amino acid chain will also change.
30:22And this will alter the bonding. Let's
30:24say
30:25amino acid is bonding with another amino
30:28acid.
30:29If we change the pH,
30:31this will alter the bonding, and the
30:33change of shape of the active site will
30:36be also present in this.
30:38This sentence alone answers many IMAT
30:41questions.
30:42The final part about
30:45enzyme is competitive and
30:48non-competitive inhibition.
30:51Competitive
30:53versus non-competitive
30:56inhibition. So,
30:58say slowly and clearly, what is
31:00competitive inhibition? The inhibitor
31:02competes with the substrate for the
31:04active site.
31:06And in case of competitive inhibition,
31:09increasing the substrate
31:13can reduce the inhibition.
31:16In case of competitive inhibition, let's
31:18say you have substrate, I mean reactant,
31:20let's say A and B, and it is making C
31:23and D. These two will be called
31:25substrate. If you increase the substrate
31:27concentration, then the inhibition will
31:30be reduced gradually. That means that if
31:34in case of competitive inhibition, if
31:37you increase the substrate
31:39concentration, eventually there will be
31:41reduction in
31:43the inhibition.
31:45And what about non-competitive?
31:48In case of non-competitive inhibition,
31:50the inhibitor
31:52will bind to an allosteric site.
31:55In case of non-competitive inhibition,
31:58you might increase the substrate
32:00concentration, but the inhibition cannot
32:03be overcome.
32:04And I met
32:06will ask you this question as if it's
32:08your second nature.
32:10So, we have covered so many things about
32:12enzyme. Let's review them one by one.
32:16And we have said what enzymes do.
32:19Enzymes are biocatalyst.
32:21They will increase the reaction rate.
32:23Remember, they will not decrease. They
32:25will only increase the reaction rate.
32:27How? By lowering activation energy.
32:30And after the reaction is complete, the
32:33enzymes will not be consumed.
32:36And what are the effects of temperature
32:37and pH effects? I met with love crafts.
32:40We will
32:42solve it and optimum pH temperature
32:44interpretation. And I met will also test
32:47the kind of data reasoning. So, what is
32:49the key logic that we need to review? If
32:51we increase the temperature, the kinetic
32:54energy will increase and the collision
32:56frequency will also increase up until
32:59the optimum temperature, right?
33:02If we increase the temperature beyond
33:04the optimum temperature, enzyme will
33:07lose its active site and pH changes
33:10ionization of amino acid, that's why
33:12there will be an optimum pH, too.
33:14We have covered the competitive versus
33:16non-competitive inhibition. In case of
33:19non-competitive,
33:21let's cover the non-competitive first.
33:23If you increase the concentration of the
33:26substrate, you will not be able to
33:29increase the rate of reaction or you
33:32will not be able to reduce the
33:35inhibition. But, competitive inhibition
33:38gives you that opportunity. If you
33:40increase the substrate concentration,
33:42then the inhibition effect can be
33:45controlled or reduced.
33:47So, we have covered basic topics now and
33:50we need to solve some questions.
33:53The first question that we are seeing, I
33:56will give you 15 seconds.
33:58The question is,
34:00which property of water is most
34:02important when heat is lost from human
34:05skin during sweating?
34:09Pause the video, attempt the question,
34:11then come back for solutions.
34:14Okay, we have given you the time.
34:17Okay, now let's solve the question. We
34:19have said that
34:21there is a property called latent heat
34:25of vaporization.
34:27That means water will absorb some
34:29temperature or heat before it changes
34:33its physical state. Heat that water can
34:37hold
34:39that heat is called latent heat. And
34:42that's why the answer would be latent
34:43heat of vaporization.
34:46Okay, the next question.
34:48The question states a polysaccharide is
34:50made by joining five glucose monomers.
34:53What is its chemical formula? The
34:55options will look like this. C6
34:58H12 O6
35:00then C30 H52 O26
35:05Let's put the third option C30 H60 O40
35:11then C5 H60 O5. The final one is
35:16CH then N-1
35:20O
35:21then put a bracket
35:24and two another bracket.
35:27How to solve this?
35:29We need to remember when one glucose
35:32monomer
35:34attaches with another monomer we will
35:37lose one water
35:39molecule. But we see that five glucose
35:42monomers are attaching here. That's why
35:45we will subtract four water molecules.
35:49We need to keep it in mind. Now, let's
35:52write the formula of glucose that will
35:54be C6 H12
35:57O6
35:59multiply it with five. That would give
36:01us C30
36:04then H60 and O
36:0830.
36:09Remember we need to subtract four water
36:11molecules. We will subtract it. It will
36:14be like 4 H2O.
36:16And it will give us if we count it
36:19properly then C30 H52
36:23and O26.
36:26That's why our answer would be option B.
36:30Now let's go with question three.
36:32We see that there is a sequence of C C G
36:36T T A T T G A and the sequence is found
36:40on one strand of deoxyribonucleic acid
36:42helix. Which sequence is on the
36:45complementary strand? To solve this
36:47question, we must remember C will
36:51have bond with G and A will have bond
36:54with T. So let's write under C we will
36:58write G another G C
37:01then A another A another T then two more
37:07A's
37:10and C and T. Let's see where we can find
37:14this option. We see that we found this
37:16option in option A. That is G G C A A T
37:22A A C T. Let's move to the next
37:23question.
37:25We remember that in case of competitive
37:28inhibition
37:29if you increase the substrate
37:31concentration, then you can reduce
37:34the inhibition. So keeping that in mind,
37:37we need to read five of the options.
37:41The option one or option A has competes
37:44with substrate for the active site.
37:47Is that true?
37:49Yes, this is true. In competitive
37:52inhibition, the inhibitor will have
37:54competition with the substrate for
37:56active site. We need to remind you the
37:58active site means the place of the
38:00substrate where
38:02the enzyme will get attached. Another
38:05term is allosteric site. In case of
38:08allosteric site, there will be another
38:11regulatory protein or controller
38:13molecule that can change the shape of
38:16the active site of an enzyme. All right?
38:19Don't get confused between active site
38:21and allosteric site. As we have gotten
38:24option A as our correct answer, we will
38:26not look for the other options.
38:29Even after that, I can explain why the
38:32other options are not correct. In option
38:34B, we see that
38:36it is said that the inhibitor will bind
38:39to substrate. No, this is not true. This
38:42is false. It will not bind to the
38:44substrate.
38:45And option C, the inhibitor binds to
38:48allosteric site. No.
38:52And
38:53the other options are not correct as
38:55well.
38:56Now, let's move to question five.
38:59What does option five say?
39:02Option five says that when investigating
39:05enzyme activity, enzyme P has optimum pH
39:08of 4.5 and enzyme Q has optimum pH of
39:129.5. Which statement must be correct?
39:15Okay.
39:16Option A says that both enzymes have the
39:19same optimum temperature. Is that true?
39:22No.
39:23Because they have different optimum pH,
39:26they will not have the same optimum
39:28temperature. What about option B? Enzyme
39:31P is denatured at pH 4.5. No.
39:36It is not denatured. Enzyme P will show
39:40maximum activity in case of pH 4.5. What
39:44about option C? Enzyme Q is more active
39:46in acidic conditions.
39:48Enzyme Q has optimum pH of 9.5, which is
39:52an alkaline pH. That's why this is not
39:55correct as well. What about option D?
39:58Option D says changing pH changes
40:01ionization of amino acid side chains and
40:04can alter the active site. This is true.
40:06We have already said. And what about
40:08option E? pH doesn't affect enzyme
40:10activity. Not true. pH can significantly
40:13affect enzyme activity. That's why our
40:15answer would be D.
40:17Now, our next part
40:19is full of solutions.
40:22I will give you some mini homeworks
40:25from the papers. Practice the patterns.
40:28Practice the deoxyribonucleic acid base
40:30percentage, hydrogen bonds,
40:33phosphodiester bonds counting, and also
40:35enzyme pH and temperature graph
40:37interpretation. If you like my lecture,
40:40please do
40:42put a like and subscribe. And if you
40:44want to buy my bundle, I have
40:47a PDF. Thank you. See you in the next
40:50lecture.

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